Effect of symmetry and substituents of cobalt based phthalocyanines in aptasensor design for the electrochemical impedimetric detection of the human epidermal growth factor receptor 2

Surface functionalization in biosensor design remains the major contributor to biosensor efficiency and selectivity. In electrochemical biosensor design, the surface is usually functionalized to achieve immobilization of the biorecognition element as well as electron transfer mediation for signal amplification. An asymmetric cobalt tris-(acetylphenoxy)-mono-phenoxyacrylic acid phthalocyanine (CoMPhAaPc) and a symmetric cobalt tetra-acetylphenoxy phthalocyanine were used for immobilization of HB5 aptamer and signal amplification towards the electrochemical detection of the human epidermal growth factor 2 (HER2). The efficiency of the two phthalocyanines is compared in relation to the substituents and symmetry. The two phthalocyanines were further coupled with sulphur nitrogen graphene quantum dots (SNGQDs) via x-x interactions, for enhanced activity and performance towards HER2 detection. The efficiency of the designed sensors was tested using the detection of HER2 in human serum. The best performance was observed for the SNGQDs(x) CoMPhAaPc/HB5 (amide) with limit of detection value of 0.0027 ng/mL and sensitivity of 72,253 c >= ng-1mL. Considering these results, the aptasensors demonstrate great potential for improved monitoring of human epidermal growth factor receptor 2 levels for the management of breast cancer.